Consider a spring that does not obey hooke's law very faithfully. one end of the spring is fixed. to keep the spring stretched or compressed an amount x, a force along the x-axis with x-component fx=kx−bx2+cx3 must be applied to the free end. here k=100n/m, b=700n/m2, and c=12,000n/m3. note that x> 0 when the spring is stretched and x< 0 when it is compressed. (a) how much work must be done to stretch this spring by 0.050 m from its unstretched length? (b) how much work must be done to compress this spring by 0.050 m from its unstretched length? (c) how much work must be done to move the spring from being compressed by 0.070 m to being stretched by 0.030 m, assuming the end moves with constant speed during the motion?